Control system



March 8, 1938. '51 R RHEA 2,110,718

CONTROL SYSTEM Filed April 29, 1936 Inventor: Thomas R. Rhea tzg j yw S ttorn el Patented Mar. 8, 1938 QJLMWM @iiN'ilitQi. SYSTEM New York Appiication April 29, 1936, Serial No. 76,992

7 (Oiaims.

This invention relates to control systems, more particularly to control systems for apparatus having an element operating on a strip of mate= rial and it has for an object the provision of a simple, reliable and efiicient control system of this character.

In one of its aspects, the invention relates to control systems for a shear that cuts a moving bar or strip of material into predetermined lengths, and a more specific object of the invention is the provision of means for introducing a time delay between'the instant the material contacts a flag switch and the initiation of the cutting operation that is proportional to the speed of the material. The length of the ma terial cut off must be adjustable and for this reason the duration of the time delay must also be adjustable.

In carrying the invention into eifect in one form thereof, means are provided for feeding the strip of material to the element operating thereon, and time element means actuated in accordance with the speed of the strip are provided for controlling the operation of the operating element.

In illustrating the invention in one form thereof it is shown as embodied in apparatus for controlling the operation of a shear for cutting predetermined lengths from an advancing bar or strip of metal.

For a better and more complete understanding of the invention, reference should now be had to the following specification and to the accompanying drawing, the single figure of which is a simple, diagrammatical illustration of an embodiment of the invention.

Referring now to the drawing, a strip of metal iii is being delivered from the rolls ll of the last stand of a rolling mill to apparatus having an element such as the shear [2 operating thereon at intervals to cut predetermined lengths from the strip. The shear I2 is operated by suitable means illustrated as a solenoid I3. In actual practice the structure of the shear and operating mechanism may be quite different from the structure illustrated. For example, the shear blades may be parts of continuously rotating rollers and the strip may be carried in a trough which is moved laterally by suitable means such as a solenoid so that the strip is carried into the shear and reversed. In the interest of simplification, the solenoid i3 is lllustrated as actuating a blade of the shear, but it will be understood, that it may be used merely to move the strip into the shear.

The rolls ii of the last mill stand are driven by suitable driving means illustrated as an electric motor it, supplied from a source of power represented by supply lines l5.

The shearing operation is initiated by suitable r means illustrated as a flag switch l6. For the d purpose of controlling the length of the material cut from the strip means are provided for introducing an adjustable time delay between the actuation of the flag switch and the operation 10 of the shear. This means is illustrated as an adjustable cam switch i1 having a stationary contact member He and a rotatable cam contact member lib which is biased to an initial position by means of a spring '10.

As shown, the rotatable member i lb is arranged to be driven in accordance with the speed of the strip. For this purpose, an electrical motion transmitting system comprising a transmitting device it connected to be driven by the last finishing stand of the mill, a receiving device i9, and a clutch 2!] for connecting the rotatable contact member to the rotor member of the receiving device I19. The transmitting device l8 comprises a stator member I88 provided with a distributed three element winding that is physically similar to a three phase winding, and a rotor member 681; provided with a single phase winding (not shown) in inductive relationship with the stator winding. The receiving device i9 is in all respects identical with the transmitting device. As indicated the terminals of corresponding legs of the stator windings are connected together by means of conductors 2i, and the single phase rotor windings are connected to a source of single phase alternating voltage represented by supply lines 22. The currents flowing in the rotor windings of both devices induce voltages in the stator windings. When the axes of the rotor windings are in positions of correspondence the voltages induced in the stator windings are equal and opposite and no currents flow in the conductors 2i. However, if the rotor of one of the devices isdisplaced relatively to the other, the voltages induced in the stator windings become unbalanced causing circulating currents to flow in the stator windings and conductors 2 i As a result of these currents a torque is produced between the stator and rotor windings of the other device which causes its rotor to turn to a position of correspondence with the rotor that was turned. Thus, it will be seen that if the rotor member of transmitting device I8 is rotated, the rotor member of receiving device I9 will reproduce the motion of the transmitter.

The rotor member of the transmitter is connected through gearing 23 to the motor [4 that drives the rolls ll of the finishing stand, and consequently the rotor of the receiver rotates at a speed dependent upon and proportional to the speed of the strip.

Suitable means illustrated as an electromagnetically actuated relay 24 are provided for energizing the electromagnetic clutch to connect the rotating contact member lb of the time delay device to the rotor of the receiver in response to actuation of the flag switch l6 by the end of the strip. It will be observed that the stationary member 11. of the time delay device is provided with an adjustable contact member "a. By screwing this member inwardly or outwardly the time interval for rotation of the rotatable contact member from its zero position until contact is made with the stationary contact can be varied as desired.

An electromagnetically actuated relay 25 serves to energize the operating solenoid iii of the shear mechanism in response to the contact closing operation of the time delay device II. In order to prevent repeated operation of the shear before the flag switch has been released, a special interlocking relay 26 is provided. Relay 26 is designed to have a time delay in its drop-out operation that exceeds the time required for relay 24 to close its contacts in response to energization.

With the foregoing understanding of the apparatus and its organization, the operation will readily be understood from the following detailed description.

When the strip I0 does not engage the flag switch, the movable contact member bridges the stationary contact members to complete an energizing circuit for the special interlocking relay 26 that is readily traced from the positive side of a supply source, through contacts l6. and operating coil of relay 26 to the negative side of the source. Accordingly, relay 26 is normally energized and its contacts closed. The end of the advancing strip strikes the flag switch l6 causing the movable contact member vto open the contacts l6. and to close contacts I611. The opening of contact l6. interrupts the energizing circuit of relay 26. However, since relay 26 is designed to have a time delay in its drop-out action, its contacts remain closed until after the movable contact member has engaged stationary contacts l6b to complete an energizing circuit for relay 24 and the latter has had time to close its contacts and complete a locking circuit independent of the contacts of relay 26. The energizing circuit for relay 24 is traced from the positive side of the source through contacts lib bridged by movable contact member of the flag switch l6, stationary contacts of relay-26 bridged by movable contact member, operating coil oi. relay 24, conductor 21 and lower stationary contacts 25: of relay 25 bridged by a movable contact member to the negative side of the source. The locking circuit for relay 24 'is completed through upper stationary contact members 24a bridged by the upper movable contact member. At the expiration oi! the time delay for which relay 26 is designed, its contact opens.

In the closed position of relay 24, the lower movable contact member bridges stationary contact members 24b to complete an energizing circuit for the electromagnetic clutch 20 which responds to connect the rotatable contact member l'lb of time delay device i1 to the rotor member of motion receiving device l9. Since the rotor member of the receiving device I9 is rotating at a speed proportional to the velocity of the strip III, the movable contact member I'Ib is rotated in a counter-clockwise direction from its zero position. After a time delay, dependent upon the speed of the strip and the setting of the adjustable contact member l'ld, the movable contact member ilb engages the stationary contact member to complete an energizing circuit for the operating coil of relay 25. This circuit is seen to extend from the positive side of a source to the movable and.stationary contacts of time delay device [1, conductor 28 and operating coil of relay 25 to the negative side of the source. Relay 25 in responding to energization causes the separate stationary contact 25! to complete a locking circuit for the operating coil independent of the contacts of the time delay device IT. The lower stationary contacts of this relay are also opened to interrupt the locking circuit of relay 24 which thereupon opens both pairs of stationary contacts. contacts 241, the energizing circuit for the clutch 20 is interrupted thereby disconnecting the rotatable contact member Ilb of the time delay device H from the rotor member of the motion receiving device I9 and the contact member "b is returned by means of the biasing spring I'Ic to its zero position.

In the closed position of relay 25, the intermediate stationary contacts 25c are bridged by the lower movable contact member to complete an energizing circuit for the operating solenoid i3 of the shear mechanism. As pointed out in the foregoing, the solenoid I3 may be regarded either as the means for actuating the shear to sever the strip ID or it may be regarded as the means for moving the trough which carries the strip I0 so that the strip is moved into the shear and severed. From either point of view, it will be seen that energization of the solenoid l3 causes the strip to be severed. When the shearing operation is completed, the movable contact member i3. of the shear limit switch is moved out of engagement with stationary contacts I3, thereby interrupting the locking circuit for the relay 25. In responding to deenergization, relay 25 opens its stationary contacts 25b and also opens stationary contacts 25c to interrupt the energizing circuit for the solenoid I3, thereby resetting the shear operating mechanism for the next out. It will also be observed that in the deenergized condition of relay 25, the lower stationary contact members 25a are bridged by the lower movable contact member thereby partially completing an energizing circuit for the operating coil of relay 24. However, no new signal for the operation of relay 24 will be obtained even though the movable contact member of the flag switch I6 is still maintained in engagement with stationary contacts I61, because relay 26 is deenergized and its contacts opened, thereby preventing relay 24 from being energized until the flag switch l6 has been restored to its initial position. It will be noted that this provides an important function in keeping the shear from operating, even though the flag switch is still maintained in the operated position at the completion of a cut.

Although in accordance with the provision of the patent statutes, this invention is described as In opening the lower pair of stationary embodied in concrete farm, it Wit be understood that the apparatus and connections shown a merely iilmtrative and that the im/enticm is it J limited t veto since 21 times an mcdifica- 5 will readiiy s skilled in the art true spirit of this t ed claims.

and. sta ic said to sever said. strip, and mews 101' e 25 time interval of said time element de to control the length of strip cut shear.

3. A control 1" said electromagrie eby tc pre Lon-ed switch 6. A control system. t a. sheer t P like ieteri i com vice actuated by said. strip, an electric Tray device for efifectii'ig actuation cf 3 to sever said strip, said deity dot. prising a stationary contact me 35 able ccntact member separateci f) ievice,

tionary member, driving" means onere A c oi I03. 2,

corriance with the speed of said strin trolled. by said switching clevi said movable member to said Qr 01' meter e acccrda said strip a time 1 switching device, at:

We]. act-ca means for V? thereby to determine the length s said sheer.

L. A control system for a shear &1 operating on a strip of material ccrcgn n ing means operated in accordance i1 ch end interlocking contact device 1 clutch.

THOIVMAS R. s 

